CN112005171A

CN112005171A - Method, measurement system, and lithographic apparatus

Info

Publication number: CN112005171A
Application number: CN201980025846.1A
Authority: CN
Inventors: F.特鲁贝尔; C.费策尔
Original assignee: Carl Zeiss SMT GmbH
Current assignee: Carl Zeiss SMT GmbH
Priority date: 2018-04-16
Filing date: 2019-04-15
Publication date: 2020-11-27
Also published as: US20210026252A1; KR20200143423A; US11163239B2; TWI810279B; TW201944178A; EP3781988A1; DE102018205714A1; EP3781988B1; WO2019201843A1

Abstract

The invention discloses a method of determining a position of an anomaly (500) in a path of travel (x, y) of an optical component (202), the optical component (202) being in a lithographic apparatus (100A, 100B) or being used in the lithographic apparatus (100A, 100B), the method comprising the steps of: a) in at least one first degree of freedom (F)_x，F_y) Moving the optical component (202), b) in at least one second degree of freedom (F)_Rz) Detecting a movement (R) of the optical component (202)_z) And/or a force (M) acting on the optical component (202)_z) And c) determining the location of the anomaly (500) as beingThe movement (R) detected in step b)_z) And/or the force (M) detected in step b)_z) As a function of (c).

Description

Method, measurement system, and lithographic apparatus

The present invention relates to a method of determining the position of an anomaly in a lithographic apparatus or in a path of travel for an optical component of a lithographic apparatus. Furthermore, the invention relates to a measurement system and a lithographic apparatus.

This application claims priority from german patent application DE 102018205714.1 (filed 2018 on 16/4), the entire contents of which are incorporated herein by reference.

Microlithography techniques are used to produce microstructured components, such as integrated circuits. A microlithography process is carried out using a lithographic apparatus having an illumination system and a projection system. An image of the mask (reticle) illuminated by the illumination system is in this case projected by means of the projection system onto a substrate (for example a silicon wafer) which is coated with a photosensitive layer (photoresist) and which is arranged in the image plane of the projection system, in order to transfer the mask structure to the photosensitive coating of the substrate.

In lithographic apparatus, in particular in Extreme Ultraviolet (EUV) lithographic apparatus and mainly in illumination lenses, modules are used which contain a plurality of optical components which are actively adjusted, in particular by means of Lorentz (Lorentz) actuators. The optical component comprises in particular a mirror.

The optical components must be able to be positioned within a specified multi-dimensional travel path, particularly in six degrees of freedom. The specification of the travel path provides both minimum and maximum travel paths. In this case, the maximum travel path must be such that the corresponding optical component does not collide with the delimitation (delimitation) in an uncontrolled manner and thus lead to damage. The cause of such a collision may be, for example, electromechanical instability, incorrect operation, or vibrations during transportation of the corresponding lighting lens.

Therefore, mechanical delimitation of the travel path of the mechanically constrained optical component has become a known technique.

Typically, this mechanical delimitation provides an air gap between the optical component and an end stop (also referred to as mechanical end stop) mounted on the support frame during adjustment operations of the lithographic apparatus. In the event of a defect, the optical component strikes the end stop. However, the complete travel path can only be used with a predetermined minimum force consumption if the air gap is free of particles. Although various measures are implemented in EUV lithography devices in order to avoid contamination, it can nevertheless occur that such particles enter the corresponding air gap.

Yet another scenario where a full travel path cannot be used is a flaw in the air gap side coating on the optical component or end stop. For example, the coating may have flaking, inclusions, or inhomogeneities.

Finally, if the mounting of the end stop relative to the optical component is made by mistake, the complete travel path may also be rendered unusable.

Since the break time in the case of a lithographic apparatus results in a large economic loss, it is desirable to detect the aforementioned anomalies as quickly as possible, which lead to premature contact and thus to an undesirable restriction of the travel path.

On this background, it is an object of the present invention to provide an improved method of determining a position of an anomaly in a lithographic apparatus or in a travel path for an optical component of a lithographic apparatus. Furthermore, it is intended to provide an improved measurement system and an improved lithographic apparatus.

Accordingly, there is provided a method of determining the location of an anomaly in a lithographic apparatus or in a path of travel for an optical component of a lithographic apparatus, comprising the steps of:

a) moving the optical component in at least one first degree of freedom,

b) detecting movement of the optical component and/or forces acting on the optical component in at least one second degree of freedom, an

c) Determining the position of the anomaly as a function of the movement detected in step b) and/or the force detected in step b).

The idea of the invention is that by observing the second degree of freedom of the optical component, which is a different degree of freedom from the first degree of freedom, conclusions are drawn about anomalies in the first degree of freedom. Therefore, the corresponding abnormal position can be quickly determined, thereby reducing the interruption time of the photoetching device.

"travel path" is understood to mean a series of setpoint positions of the optical component.

An "anomaly (anomaly)" is understood to mean a structural cause, the consequence of which is that the optical component at least partially cannot move along the travel path (i.e. its setpoint position deviates from its actual position by a predetermined value), or that the travel path can only travel in a manner that is more force consuming (that is not tolerable, for example, for thermodynamic reasons) (i.e. the setpoint force deviates from the actual force by a predetermined value).

The anomaly may be selected, for example, from:

-particles in the air gap; this may be hard or soft particles. If the size of the hard particles can no longer be compensated by, for example, a (soft) coating in the form of an elastomer, in particular a fluoroelastomer (in particular available under the trade name Viton) on the optical component or on the end stop, the hard particles will lead to a defective condition. If, in particular, no (soft) coating is provided at all on the optical component or on the end stop, soft particles will lead to a defective condition.

Coating imperfections, in particular including flaking, inclusions or inhomogeneities, on the end stop and/or on the optical component; and

-defect alignment of the end stop relative to the optical component.

The first and second degrees of freedom can be selected in each case from up to six degrees of freedom. The six degrees of freedom include three translational and three rotational degrees of freedom.

The term "moving" optical component is to be taken to mean a change in its actual position. The actual position change is accounted for by translation and/or rotation vectors (up to six degrees of freedom). This change in actual position is the result of a comparison of the two actual positions of the optical component at different points in time.

The "detection movement" of the optical component is considered to mean that the movement of the optical component is detected indirectly or directly by means of sensor members (means). The movement is detected by detecting the actual position of the optical component at least two different points in time.

A "determined location" of an anomaly may include, for example, locating the anomaly in a coordinate system. Therefore, an output can be made that describes the position of the anomaly in x, y, and z coordinates. The coordinate system may be linked to the optical component, the measurement system or the lithographic apparatus (in particular to the sensor frame thereof). In particular, the dispensing of one or more end stops delimiting the movement of the optical component can be performed.

In the present case, "end stop" is understood to mean the mechanical delimitation of the travel path of the optical component.

Within the scope of the force referred to in the present case, this also always covers the possibility of detecting a torque instead of (or in addition to) a force.

Preferably, in step b), the movement of the optical component and the force acting on the optical component are detected in at least one second degree of freedom. By monitoring these two parameters, the location of the anomaly can be determined even more quickly.

Within the scope of the method steps indicated by a), b) and c) in the present case, this is only used for a better distinction. Thus, the specified order of steps is not predetermined. Whereby the designation of an altered method step (method step a) into method step b)) is not excluded, the insertion of further method steps (for example, the insertion of a new method step between method steps a) and b), wherein then the new method step is designated method step b) and the earlier method step b) is designated method step c), and the addition of further method steps (for example method step d)) are covered by the present invention.

According to one embodiment, the first or second degree of freedom is a translational (translational) degree of freedom and the respective other degree of freedom is a rotational degree of freedom.

Applicant's experiments have shown that the anomaly position can be best determined in the translational degree of freedom by reference to the rotational degree of freedom and vice versa.

According to a further embodiment, the first degree of freedom is a translational degree of freedom and the second degree of freedom is a rotational degree of freedom.

In this case, therefore, the first degree of freedom describes a translation of the optical component along a translation vector. The second degree of freedom describes the rotation of the optical component about the corresponding rotation vector. The translation vector and the rotation vector are preferably oriented perpendicular to each other. In particular, in step a), the optical component can be moved in at least one first and one second degree of freedom, wherein the first and second degree of freedom are in each case translational degrees of freedom. In this case, the corresponding translation vectors of the first and second degrees of freedom are oriented perpendicular to each other. Thus, the translation vector describes a plane. Also in this case, step b) involves, for example, detecting the movement of the optical component and/or the force (and/or torque) acting on the optical component in at least one third degree of freedom. In this case, the third degree of freedom is a rotational degree of freedom. The rotational degree of freedom is illustrated by a rotation vector oriented perpendicular to the aforementioned plane defined by the two translation vectors. Experiments by the applicant have revealed that in this embodiment it is possible to determine the position of an anomaly in the plane in a particularly simple manner by means of a rotation about a rotation vector perpendicular to the plane and/or by means of a detected torque about a rotation vector perpendicular to the plane. In this case, the travel path of the optical component lies in the plane.

According to a further embodiment, moving the optical component according to step a) is limited by at least one end stop.

In particular, as explained above in step a), the optical component can also be moved in at least one first and one second degree of translational freedom. Each of these degrees of freedom may be limited by a corresponding end stop. This covers the fact that one of the same end stops (mechanical stops) can limit two or more degrees of freedom, i.e. act like at least two end stops in different degrees of freedom.

According to a further embodiment, moving the component in step a) is performed according to a predetermined path or a predetermined movement pattern.

The predetermined path or the predetermined movement pattern may be stored, for example, on a storage unit, in particular a hard disk or a solid state drive.

According to a further embodiment, the predetermined movement pattern has a plurality of translational movements of the optical component in a plane, said translational movements starting from a central point (centre point).

Thus, the predetermined movement pattern may have a number a of radial lines (spokes), in particular (of the imaginary wheel). The radiation lines can in each case be at equal angles to one another. Depending on the requirements/application, the angles may also not be equal. A can be, for example, greater than or equal to 3, 4, 7, 8, 9, 12, 13, 15, 16, or 20, where a is an integer.

According to a further embodiment, the determination of the position of the anomaly in step c) is additionally implemented as a function of a predetermined path or a predetermined Movement pattern (BM) and/or as a function of the actuation force for moving the optical component in step a).

In other words, therefore, in step c), not only the abnormal position is determined as a function of the movement detected in step b) and/or the force detected in step b), but also more parameters are taken into account. According to an embodiment of the invention, said further parameter is a predetermined path or a predetermined movement pattern or an actuation force. In this case, the actuating force can be taken into account in step c) in two different ways. First, in the form of a setpoint actuation force, i.e. the force of a command actuator that moves the optical component in at least one first degree of freedom. For example, this force may be read from a corresponding control device (device). Secondly, it is possible (or in addition) to take into account the actual actuation force measured in step c) (by the sensor means).

According to a further embodiment, a movement of the optical component according to step a) is detected, and the determination of the abnormal position in step c) is additionally implemented as a function of the detected movement.

In this embodiment, the movement of the optical component in step a), for example in real time, is detected by a sensor and taken into account when determining the position of the anomaly in step c). In this case, therefore, what is considered in step c) is indeed not a movement of the setpoint commanded for the corresponding actuator, or a feedforward control and/or regulation unit connected upstream thereof, but an actual movement.

According to a further embodiment, the determination of the abnormal position in step c) is additionally implemented as a function of the position of a rotation vector, which accounts for the rotation of the optical component relative to the at least one end stop.

The position of the at least one end stop, the relation of the (predetermined) movement of the optical component and the (predetermined) actuation force allow a quick conclusion to be drawn on the determination of the abnormal position.

According to a further embodiment, it is determined in step c) that at least one end stop has an anomaly.

Therefore, the abnormality thus occurs and is assigned to the end stop. The anomaly is typically assigned to one of a plurality of end stops.

According to a further embodiment, at least one end stop has a peg (peg) that engages in a cut-out of the optical component. There is an annular gap between the notch and the peg.

In the present case, the "ring gap" is also referred to as an "air gap". However, in general, a vacuum, in particular a high vacuum, is usually present in the annular gap. At least two, three or more end stops, each having the aforementioned configuration, may also be provided. This type of end stop has the advantage of allowing an accurate delimitation of the travel path.

According to a further embodiment, the anomaly is a particle in the annular gap, a coating defect of the cut-out and/or the peg, and/or a mis-alignment of the peg with respect to the cut-out.

Where multiple end stops are provided, the anomaly may be a particle in the at least one annular gap, a coating defect in the at least one cut and/or in the at least one peg, and/or a mis-alignment of the at least one peg relative to the at least one cut.

According to a further embodiment, the optical component is a mirror, a lens element, a grating or a lambda plate.

The mirror is particularly suitable for EUV lithography, whereas the lens element is particularly suitable for Deep Ultraviolet (DUV) lithography.

According to a further embodiment, the cut-outs are formed in the optical element and the pegs are formed on the support frame.

The cut-out may be, for example, a cylindrical (particularly cylindrical (i.e. hole or hole)) cut-out, and the peg may be a cylindrical (particularly cylindrical) peg. The cut-outs may be formed as continuous or discontinuous (blind) cuts.

Furthermore, a measurement system for determining an abnormal position in a lithographic apparatus or in a travel path of an optical component for a lithographic apparatus is provided. The measurement system comprises the following: an actuator for moving the optical component in at least one first degree of freedom; a sensor unit for detecting a movement of the optical component and/or a force acting on the optical component in at least one second degree of freedom; and a computer unit for determining the position of the abnormality as a function of the movement detected in step b) and/or the force detected in step b).

This type of measurement system can be implemented as a stand alone solution or integrated in a lithographic apparatus. In the case of a stand-alone solution, the measurement system can be used, for example, in this way: if the lithographic apparatus determines an anomaly in the path of travel of the optical component, a module comprising the optical component and the end stop is detached from the lithographic apparatus and inserted into the measurement system. The measurement system then processes the foregoing method steps to determine the location of the anomaly.

Likewise, however, the lithographic apparatus may also incorporate the measurement system in an integrated manner. Advantageously, the lithographic apparatus may indicate a defect at the determined location in the output device. Thus, the repair can be made in a targeted manner.

Thus, the following are provided: a lithographic apparatus includes an optical component and a measurement system configured to determine an abnormal position in a travel path of the optical component.

The features and advantages described for the method apply correspondingly for the measurement system and the lithographic apparatus and vice versa.

The word "a" or "an" in the present context should not necessarily be construed as limited to only one element. Rather, multiple elements (e.g., two, three, or more) may be provided so long as the converse is not indicated.

Further possible implementations of the invention also include combinations of features or embodiments not explicitly mentioned above or described below in connection with the exemplary embodiments. In this case, the person skilled in the art will also add individual aspects as modifications or additions to the basic forms of the invention.

Further advantageous configurations and aspects of the invention are the subject matter of the dependent claims of the invention described below and also of the exemplary embodiments. In the following description, the present invention is explained in more detail based on preferred embodiments with reference to the accompanying drawings.

FIG. 1A shows a schematic diagram of an embodiment of an EUV lithographic apparatus;

FIG. 1B shows a schematic diagram of an embodiment of a DUV lithographic apparatus;

FIG. 2 shows a portion of a measurement system according to one embodiment, in which, among other things, general optical components are illustrated;

FIG. 2A shows six possible degrees of freedom of the optical component of FIG. 2;

FIG. 3 shows section III-III of FIG. 2, partially illustrating in section one of the pegs along with a coating;

FIG. 4 schematically shows the measurement system of FIGS. 2 and 3 with other components;

FIG. 5 shows the view of FIG. 2 with a flaw;

FIG. 6 shows an exemplary movement pattern applied to the optical component in FIG. 5, wherein in particular in each case in the xy-plane, the positions moved to for the normal case and the positions moved to in the case of a defect are illustrated and a rotation about the z-axis is indicated;

FIG. 7A shows a graph showing rotation or torque versus actual position for the radial lines in FIG. 6;

FIG. 7B shows deriving rotation or torque about the position shown with reference to FIG. 7A; and

FIG. 8 illustrates, in a flow chart, a method in accordance with one embodiment.

In the drawings, the same elements or elements having the same function have the same reference numerals unless otherwise indicated. It should also be noted that the illustrations in the drawings are not necessarily to scale.

FIG. 1A shows a schematic diagram of an EUV lithographic apparatus 100A, which includes a beam shaping and illumination system 102 and a projection system 104. In this case, EUV stands for "extreme ultraviolet light" and is a wavelength of operating light between 0.1nm and 30 nm. The beam shaping and illumination system 102 and the projection system 104 are provided in vacuum enclosures (not shown), respectively, each evacuated by means of an evacuation device (not shown). The vacuum housing is surrounded by a machine room (not shown) in which drive means for mechanically moving or setting the optical elements are provided. Also, power controllers and the like may be provided in this machine room.

The EUV lithography apparatus 100A includes an EUV light source 106A. A plasma source (or synchrotron) emitting radiation 108A in the EUV range (extreme ultraviolet range), i.e. for example in the wavelength range of 5nm to 20nm, may for example be provided as EUV light source 106A. In the beam shaping and illumination system 102, EUV radiation 108A is focused and a desired operating wavelength is filtered out of the EUV radiation 108A. The EUV radiation 108A generated by the EUV light source 106A has a relatively low air transmissivity and therefore evacuates the beam-guiding space in the beam shaping and illumination system 102 and the projection system 104.

The beam shaping and illumination system 102 illustrated in fig. 1A has five

mirrors

110, 112, 114, 116, 118. After passing through the beam shaping and illumination system 102, the EUV radiation 108A is directed onto a photomask (referred to as reticle) 120. The photomask 120 is also formed as a reflective optical element and may be disposed outside of the

systems

102, 104. Again, EUV radiation 108A may be directed onto the photomask 120 by way of a mirror 122. The photomask 120 has a structure that is imaged onto a wafer 124 or the like in a demagnified fashion by the projection system 104.

Projection system 104 (also referred to as a projection lens) has six mirrors M1-M6 for imaging photomask 120 onto wafer 124. In this case, the individual mirrors M1 to M6 of the projection system 104 may be symmetrically arranged with respect to the optical axis 126 of the projection system 104. It should be noted that the number of mirrors M1-M6 of the EUV lithography apparatus 100A is not limited to the number represented. A greater or lesser number of mirrors M1-M6 may also be provided. In addition, the mirrors M1 to M6 are typically curved on their front faces for beam shaping.

FIG. 1B shows a schematic diagram of a DUV lithographic apparatus 100B, which includes a beam shaping and illumination system 102 and a projection system 104. In this case, DUV stands for "deep ultraviolet light" and is the wavelength of operating light between 30nm and 250 nm. As already explained with reference to fig. 1A, the beam shaping and illumination system 102 and the projection system 104 may be arranged in a vacuum housing and/or surrounded by a machine room equipped with corresponding drive means.

DUV lithographic apparatus 100B has a DUV light source 106B. For example, an ArF excimer laser emitting radiation 108B in the DUV range (e.g., at 193nm) may be provided as the DUV light source 106B.

The beam shaping and illumination system 102 illustrated in fig. 1B includes a lens element 127 and/or a mirror 131 (only two such elements are shown by way of example in fig. 1B) that directs DUV radiation 108B onto the photomask 120.

The photomask 120 is implemented as a transmissive optical element and may be disposed outside of the

systems

102, 104. The photomask 120 has a structure that is imaged onto a wafer 124 or the like in a demagnified fashion by the projection system 104.

The projection system 104 has a plurality of lens elements 128 and/or mirrors 130 for imaging the photomask 120 onto the wafer 124. In this case, the individual lens elements 128 and/or mirrors 130 of the projection system 104 may be arranged symmetrically with respect to the optical axis 126 of the projection system 104. It should be noted that the number of lens elements 128 and mirrors 130 of the DUV lithographic apparatus 100B is not limited to the number represented. A greater or lesser number of lens elements 128 and/or mirrors 130 may also be provided. Furthermore, the mirror 130 is typically curved on its front face for beam shaping.

The air gap between the last lens element 128 and the wafer 124 may be replaced with a liquid medium 132 having a refractive index > 1. For example, the liquid medium 132 may be high purity water. This configuration is also referred to as immersion lithography and has improved lithographic resolution. The medium 132 may also be referred to as an immersion liquid.

Fig. 2 shows a part of a measuring system 200 according to an embodiment in a plan view.

The measurement system 200 includes an optical component 202. The optical component 202 is for example a mirror, a lens element, a grating or a lambda plate. In particular, it may be one of the mirrors 110 to 118, M1 to M6, 130, 131 or one of the

lens elements

127, 128 in the illumination system 102 or projection system 104 of the EUV or DUV

lithographic apparatus

100A, 100B, respectively, in fig. 1A or 1B.

According to an exemplary embodiment of the invention, the optical component 202 is a mirror having an optically active surface 204 (also referred to as an "optical footprint"). The optically active surface 204 may reflect EUV light during operation.

In principle, depending on the control actuator system, the optical component 202 may be moved in up to six degrees of freedom, in particular in three translational degrees of freedom F, as illustrated in fig. 2A_x、F_y、F_z(i.e. translation along the respective axes x, y, z shown in fig. 2) and three rotational degrees of freedom F_Rx、F_Ry、F_Rz(i.e., the respective rotations about axes x, y, z shown in fig. 2).

By corresponding translation vectors x, y, z (for better clarity, in the present case there is no distinction between the translation vectors x, y, z and the axes x, y, z in the figures) and rotation vectors R_x、R_y、R_z(only R is illustrated in the drawings_z) Movement of the optical component 202 in six degrees of freedom is illustrated. It should be noted that the rotation vector is in each case composed of a unit vector and an angle. The unit vectors are coaxial with the respective translation vectors (and thus, for example, translation in x and rotation about x). The angle indicates the absolute value of the rotation around the unit vector.

According to this exemplary embodiment, optical component 202 may be in two translational degrees of freedom F_x、F_yNeutral one degree of rotational freedom F_RzTo move. However, any other combination of translational and rotational degrees of freedom is also conceivable.

Measurement system 200 includes, for example, three end stops 206A, 206B, and 206C shown in FIG. 2. For simplicity, the following description is with respect to end stop 206A, and the correspondence applies to end

stops

206B and 206C. The peg 210 is fixed to the part of the support frame shown by way of example in fig. 3 and it has the reference 300. The peg 210 engages through the cutout 208 perpendicular to the plane of the drawing of fig. 2. The cut-out 208 is introduced into the optical component 202. This is for example achieved by drilling corresponding holes in the material of the mirror. Like the notch 208, the peg 210 may have a cylindrical cross-section. This is also seen in fig. 3, which shows section III-III of fig. 2. In this case, there is an annular gap 212 between the respective cutout 208 and the respective peg 210.

This results in mobility of the optical component 202 along translation vectors x and y that are oriented perpendicular to each other. The translation vectors x and y are in each case oriented perpendicularly to the corresponding central axis 214 of the peg 210. Rotation vector R_zExtending perpendicularly to the translation plane thus defined. The rotation amount indicates the rotation of the optical component 202 in the xy plane.

The end stops 206A, 206B, 206C limit the travel paths x, y of the optical component 202 due to the corresponding contact between the peg 210 and the cutout 208. In order to avoid damage to the optical component 202 due to high accelerations, the peg 210 may be provided with a (soft) coating (e.g. consisting of an elastomer, preferably a fluoroelastomer). The coating has reference 216. In contrast, in particular, the inner wall of the cutout 208 is uncoated and is therefore embodied relatively hard.

As can be seen in fig. 3, depending on the embodiment, the optical component 202 may be adjusted in up to six degrees of freedom by means of actuators 302 (two are illustrated, for example) coupled to the optical component 202 by corresponding pins 304. According to an exemplary embodiment, the actuator 302 may be utilized in a translational degree of freedom F_xAnd F_yAnd degree of rotational freedom F_RzThe optical component 202 is adjusted.

Fig. 4 shows the measurement system 200 as a block diagram, wherein the optical component 202 of fig. 2 and 3 together with the end stops 206A, 206B, 206C and determining their (mechanical) properties are illustrated in blocks.

In fig. 4, the actuator 302 of fig. 3 is also illustrated in blocks. The actuator generates a force and/or torque FM having an optical component 202 in a degree of freedom F_x、F_y、F_RzAnd at a passing actual position (e.g. x)_{Practice of}、y_{Practice of}、R_z-actual) The effect of movement in the program of (1). In this case, x_{Practice of}Indicates the position of the optical component 202 along the x-axis, y_{Practice of}Denotes position along the y-axis, and R_z-actualIndicating the angle of rotation about the z-axis.

The measurement system 200 further comprises a sensor unit 400, such as an optical sensor. The sensor unit 400 detects the actual position x of the optical member 202_{Practice of}、y_{Practice of}、R_z-actual。

The measurement system 200 further comprises a computer unit 402. For example, in a conditioning (exposure) operation of the lithographic apparatus 100A, which is an operation or method of determining the position of an anomaly 500 in the travel path x, y of the optical component 202 described in more detail below with respect to a method of determining position (localization method) below, the computer unit determines a setpoint position (e.g., x) of the optical component 202_{Set point}、y_{Set point}、R_z-setpoint). The setpoint positions are determined according to the requirements ultimately imposed by the structure to be imaged onto the wafer 124 (see fig. 1A).

Set point position x_{Set point}、y_{Set point}、R_{Z set point}Is buffered, for example, on a storage unit 404 (e.g., a hard disk or solid state drive) of the measurement system 200. The providing unit 406 (called the set point generator) of the measurement system 200 finally locates the set point position x_{Set point}、y_{Set point}、R_z-setpointProvided to both the comparator unit 408 and the feedforward control unit 410. The comparator unit 408 is connected in terms of signaling (signaling) to a regulator unit 412 of the measurement system 200.

The regulator unit 412 regulates the manipulated variable SG₁As set point position x (for the respective degree of freedom)_{Set point}、y_{Set point}、R_z-setpointAnd the actual position x_{Practice of}、y_{Practice of}、R_z-actualAs a function of (c). For this purpose, the set-point position and the actual position are compared with each other in a comparator unit 408 and the comparison value is supplied to a regulator unit 412.

The regulator unit 412 is followed by an adding unit 414. The addition unit 414 adds the manipulated variable SG₁And the manipulated variable SG₂To form the manipulated variable SG.

Dependent on set point position x_{Set point}、y_{Set point}、R_z-setpointIn turn, the feedforward control unit 410 provides the second manipulated variable SG at the addition unit 414₂. To this end, for example, the following equations are stored on the feedforward control unit 410:

SG₂＝c*x_{set point}，

Where c is a constant. Can store y_{Set point}、R_z-setpointCorresponding equation of (2).

In other words, the feedforward control unit 410 provides the value SG for the force/torque FM to be generated by the actuator 302₂This value can be calculated simply and therefore quickly. By means of the regulator unit 412, the value SG is passed₁Correction value SG₂To thus be based on the actual position x_{Practice of}、y_{Practice of}、R_z-actualAccurately moved to a desired position x_{Set point}、y_{Set point}、R_z-setpoint。

It is noted that the control and/or adjustment of the movement of the optical component 202 may also have any other advantageous arrangement. In other words, the control and/or adjustment of the movement of the optical component 202 may be implemented by means of the

units

404, 406, 408, 412, 414 or in some other way. The arrangement illustrated here corresponds in particular to an advantage in an embodiment in which the measurement system 200 is integrated directly in the lithographic apparatus (e.g.

lithographic apparatus

100A or 100B). In this case, parts of the measurement system 200 (e.g., the feedforward control unit 410 and the regulator unit) are also used to regulate (exposure) operations.

In embodiments in which measurement system 200 is implemented as a stand-alone solution (not integrated in a lithographic apparatus), optical component 202 may be provided along with end stops 206A, 206B, 206C, and corresponding portions of support frame 300 to be inserted as modules into measurement system 200.

Specifically, independent of whether a standalone solution is implemented or integrated in the lithographic apparatus, the computer unit 402 is configured to detect and determine the location of an anomaly, such as a particle 500 (see fig. 5), in one or more of the annular gaps 212 of the end stops 206A, 206B, 206C.

If it is determined that the entire setpoint travel path of the optical component 202 cannot be obtained (first variation) or that the setpoint travel path can only be obtained with a force or torque FM that exceeds a predetermined threshold (second variation), a method of determining position (as described below) may be followed by the isolated measurement system 200 or the

lithographic apparatus

100A, 100B that includes such a system. This determination may be implemented by the computer unit 402. For this purpose, the computer unit 402 is connected to the sensor unit 400 in the case of this first variant and to the adding unit 414 in the case of this second variant, in order to detect the actuation signal SG provided for the actuator 302. These two variations are indicated in fig. 4.

Determining the location of the anomaly 500 is performed at least as the detected actual rotation R_z-actualAs a function of (c). Alternatively or additionally, in one embodiment, the sensor unit 400 may also be configured to detect the torque M about the z-axis_z-actual(not shown in FIG. 4 for clarity, but shown in FIGS. 7A and 7B). In this case, alternatively or in addition to R_zIn addition to the rotation of (a), the computer unit 402 may use the detected torque M about the z-axis_zTo determine the location of the anomaly 500 as a function thereof. Instead of the torque M, the force can also be sensed and taken into account in determining the position by the computer unit 402_z. However, this is not illustrated in more detail.

Furthermore, the computer unit 402 may be signally connected to a storage unit 416 (e.g., a hard disk or solid state drive). Predetermined movement patterns (movement patterns) BM are stored in the storage unit 416. The movement pattern BM describes, for example, a setpoint position x of the optical component 202, in particular for the position determination method_{Set point}、y_{Set point}、R_z-setpoint. These values are used as inputs or predetermined values for the feedforward control unit 410 and the regulator unit 412 to control the actuator 302. Computer unit 402 in addition to the detected movement R for determining the position of anomaly 500_z-actualAnd the detected torque M_z-actualBesides, the mobility mode BM may be used.

Finally, the spatial arrangement of the end stops 206A, 206B, 206C, the actuator 302 or its engagement point 306 on the optical component 202, and the direction of the force applied to the optical component 202 can be stored on the storage unit 416. These further parameters, denoted WP, may be provided to computer unit 402, which uses these data to determine the location of anomaly 500 as a function thereof.

The further parameters WP may likewise comprise the so-called Point of control (POC) of the optical component 202. This is the point to which the optical component 202 is attached to the coordinate system xyz with respect to all commanded and detected movements and forces/torques.

Fig. 5 shows a particle 500 in annular gap 212 of end stop 206A. The particle 500 has the following effects: the specified travel path of the optical component 202 cannot be achieved by the actuator 302 in the xy plane. This is because the particles 500 are not compressible or only partially compressible, so the coating 216 cannot fully compensate for the effect of the particles on the travel path, and the force/torque FM of the actuator 302 is insufficient to effect the desired compression.

Fig. 6 shows the movement pattern BM as stored in the storage unit 416. The radiation lines 1 to 8 are shown in this case. Each of the radiation lines represents a (translational) travel path of the optical component 202 in the xy-plane. Again, those positions that can be moved by the optical component 202 under normal conditions (non-defective conditions) are indicated in each case by N in fig. 6.

If there is an anomaly, such as a particle 500, as shown in fig. 5 (particularly at a position therein), the computer unit 402 will determine that it cannot move to the normal position N on the radiation lines 5 and 6. Instead, the calculation unit 402 determines the measured rotation R_z-actualOr the measured torque M_z-actualToo early to rise. As shown in fig. 7A, for the radiation line 5 (corresponding to the actual position of the optical component 202 in the x-direction), this rise deviates substantially from the normal case N in the defective case F.

In particular, for this purpose, the measured rotation R can be monitored_z-actualOr the measured torque M_z-actualWith respect to the actual position x_{Practice of}Derivative of (d/d)-x_{Practice of}) As shown in fig. 7B. If the derivative exceeds a predetermined threshold, the computer unit 402 determines that a fault condition F exists.

Note that fig. 7A and 7B each show only R_z-actualAnd M_z-actualA curve of (2). They are intended to be merely exemplary to illustrate the principle, and thus R is not shown_z-actualAnd M_z-actualDifferent curves of (2). In fig. 7A and 7B, "/" should be understood as "or" (or) ".

Reference is then made again to fig. 6, which also mentions the rotation R monitored on each radiation line_zTo the corresponding value of (c). For the

radiation lines

1, 2, 3, 4, 7 and 8, the values from the exemplary embodiment according to fig. 5 (ideally) are in each case 0, i.e. can be moved to the respective end position N without rotation. The situation is different on the radiation lines 5 and 6. Here, a negative rotation is sensed in each case (right-hand rule).

For radiation line 5, computer unit 402 may deduce from the control Point (POC) and the actuation force vector F5 that a particle 500 cannot be present in the annular gap 212 of end stop 206C.

From the negative rotation for the radiation line 6, still considering again the control force F6, the computer unit 402 can conclude for the radiation line 6 that the particle 500 is unlikely to be located in the annular gap of the end stop 206B.

Therefore, the computer unit 402 determines that the anomaly 500 must be caused by the end stop 206A. The determined position of the anomaly 500 (here end stop 206A) may be output, for example, in the measurement system 200 on the screen 418 (see fig. 4) or in some other manner. For example, the fact that end stop 206A has an anomaly 500 may be displayed on screen 418.

The logic according to which the end stops (here 206B and 206C) are excluded as a source of defects (i.e., affected by the anomaly 500) is a result of the torque or rotational movement induced by each actuation force F5, F6. For the sake of clarity, in this respect the axis along which these forces act is illustrated in fig. 5 by means of a dashed elongation.

It should furthermore be mentioned that instead of the computer unit 402, a staff member may perform the steps performed by the computer unit 402 by means of mental activities.

FIG. 8 generally illustrates a method of determining the location of an anomaly 500 in a path of travel (xy-plane) of an optical component 202 according to one embodiment.

Step S1 involves moving the optical component 202 in the x and y directions. This corresponds to F in the first and second degrees of freedom, respectively_x、F_yOf the mobile device (2).

Step S2 relates to F in at least one second degree of freedom_RzDetecting movement R of optical component 202_zAnd/or a torque M acting on the optical component 202_z。

Step S3 relates to determining the location of an anomaly (e.g. in the form of a particle 500) as the detected movement R_zAnd/or the detected torque M_zAs a function of (c).

Although the present invention has been described based on exemplary embodiments, it can be modified in various ways.

The units, such as the sensor unit 400, the comparison unit 408, the feedforward control unit 410, the regulator unit 412 and/or the addition unit 414, may be implemented in terms of hardware technology and/or software technology. In the case of a hardware-related implementation, the units may be implemented as devices or parts of devices, such as computers or microprocessors. In the case of an implementation of software technology aspects, the units may be implemented as computer programs or parts thereof, functions, routines or executable objects.

In the case of an implementation of the sensor unit 400 in terms of hardware technology, the sensor unit can be implemented, for example, as an optical, capacitive or inductive sensor.

REFERENCE SIGNS LIST

1 to 8 radiation lines

100A EUV lithography device

100B DUV photoetching device

102 beam shaping and illumination system

104 projection system

106A EUV light source

106B DUV light source

108A EUV radiation

108B DUV radiation

110 reflecting mirror

112 mirror

114 mirror

116 mirror

118 mirror

120 photo mask

122 mirror

124 wafer

126 optical axis

127 lens element

128 lens element

130 mirror

131 mirror

132 medium

200 measuring system

202 optical component

204 optically active surface

206A, 206B, 206C end stops

208 incision

210 stud

212 annular gap

214 center axis

216 coating

300 support frame

302 actuator

304 stud

306 junction point

400 sensor unit

402 computer unit

404 storage unit

406 providing unit

408 comparator unit

410 feedforward control unit

412 regulator unit

414 addition unit

416 storage unit

418 screen

BM mobility mode

F defect condition

FM force or torque

F_xTranslational degree of freedom in x

F_yDegree of translational freedom in y

F_zDegree of translational freedom in z

F_RxRotational degree of freedom around x

F_RyRotational degree of freedom about y

F_RzRotational degree of freedom around z

M1 reflector

M2 reflector

M3 reflector

M4 reflector

M5 reflector

M6 reflector

M_zTorque of

M_z-actualActual torque

N Normal case

R_zVector of rotation

R_z-actualActual position

R_z-setpointSetpoint movement

SG manipulated variable

SG₁First part of manipulated variables

SG₂Second part of the manipulated variable

WP more parameters

x translation vector or axis

x_{Practice of}Actual position

y translation vector or axis

y_{Practice of}Actual position

z translation vector or axis

Claims

1. A method of determining a position of an anomaly (500) in a path of travel (x, y) of an optical component (202), the optical component (202) being in or for a lithographic apparatus (100A, 100B), the method comprising:

a) in at least one first degree of freedom (F)_x，F_y) Moving the optical component (202);

b) in at least one second degree of Freedom (FR)_z) Detecting a movement (R) of the optical component (202)_z) And/or a force (M) acting on the optical component (202)_z) (ii) a And

c) determining the location of the anomaly (500) as the movement (R) detected in step b)_z) And/or the force (M) detected in step b)_z) As a function of (c).

2. The method of claim 1, wherein the first or second degree of freedom (F)_x，F_y，F_Rz) Is a translational degree of freedom and the respective other degree of freedom is a rotational degree of freedom.

3. The method of claim 2, wherein the first degree of freedom (F)_x，F_y) Is a translational degree of freedom, and the second degree of freedom (F)_Rz) Is a rotational degree of freedom.

4. The method of claim 3, wherein the movement of the optical component (202) according to step a) is limited by at least one end stop (206A, 206B, 206C).

5. The method of any one of claims 1 to 4, wherein moving the component in step a) is performed according to a predetermined path or a predetermined movement pattern (BM).

6. The method of claim 5, wherein the predetermined movement pattern (BM) has a plurality of translational movements of the optical component (202) in a plane (x, y), said translational movements proceeding from a center Point (POC).

7. The method according to claim 5 or 6, wherein the determining of the location of the anomaly (500) in step c) is additionally performed as the predetermined path or the predetermined moving moldA function of the formula (BM), and/or an actuating force (F) which is performed to move the optical component (202) in step a)₅，F₆) As a function of (c).

8. The method according to any of claims 1 to 6, wherein a movement of the optical component (202) according to step a) is detected and the determination of the position of the anomaly (500) in step c) is additionally performed as the detected movement (x)_{Practice of}，y_{Practice of}) As a function of (c).

9. The method of any one of claims 1 to 8, wherein at least one end stop (206A, 206B, 206C) is determined to have the anomaly (500) in step C).

10. The method of any of claims 1 to 9, wherein the at least one end stop (206A, 206B, 206C) has a peg (210) engaged in a cutout (208) of the optical component (202), wherein there is an annular gap (212) between the peg (210) and the cutout (208).

11. The method of claim 10, wherein the anomaly (500) is a particle in the annular gap (212), a coating defect of the notch (208) and/or the peg (210), and/or a misalignment of the peg (210) relative to the notch (208).

12. The method of any of claims 1 to 11, wherein the optical component (202) is a mirror, a lens element, a grating or a λ -plate.

13. A measurement system (200) for determining a position of an anomaly (500) in a path of travel (x, y) of an optical component (202), the optical component (202) being in or for a lithographic apparatus (100A, 100B), wherein the measurement system (200) comprises:

an actuator (302) in at least one first degree of freedom (F)_x，F_y) Moving the optical component (202);

sensor unit (4)00) In at least one second degree of freedom (F)_Rz) Detecting a movement (R) of the optical component (202)_z) And/or a force (M) acting on the optical component (202)_z) (ii) a And

a computer unit (402) determining the position of the anomaly (500) as the movement (R) detected in step b)_z) And/or the force (M) detected in step b)_z) As a function of (c).

14. A lithographic apparatus (100A, 100B) comprising:

an optical component (202), and

the measurement system (200) of claim 13, configured to determine a position of an anomaly (500) in a travel path (x, y) of the optical component (202).